The present invention relates to a device and a method for determining a voltage. In particular, the present invention relates to a method and a device for measuring a voltage in the intermediate circuit of a current converter of an electric drive system.
In electric drive systems of the type used, for example, in electrically driven motor vehicles, it is expected that the measurement of the output voltage of the traction battery or of the voltage in the intermediate circuit of an electric current converter takes place multiple times, for safety reasons. The voltage measurement takes place in the battery management system and at all consumers located on the intermediate circuit of the current converter, such as, for example, pulse-controlled inverters, DC-DC converters, and further electrified secondary units. As a rule, circuits for voltage detection divide the intermediate-circuit voltage across multiple stages in order to obtain a partial voltage which is detectable by a microcontroller. The detected signal is also converted from analog to digital, if necessary, for further conditioning, and is transferred from the high-voltage side to the low-voltage side via a galvanic isolating module.
The German patent application DE 10 2009 056 838 A1 discloses the measurement of a voltage in the intermediate circuit of a converter, wherein the voltage to be measured is used for charging at least one capacitor, for example, an intermediate-circuit capacitor. The capacitor is brought from a first state of charge into a second state of charge, and the charging time that was required is evaluated in order to determine the voltage to be measured.
Due to the strict requirements for the exact voltage detection, components having very low tolerances must be utilized for the voltage measurement. Such components are relatively expensive.
There is a demand for cost-effective, precise, and space-saving voltage detection. In particular, there is a demand for cost-effective and precise voltage detection for measuring voltage in the intermediate circuit of an electric drive system.